1. Field of the Invention
This invention relates generally to heads-up displays (HUD) and, more particularly to HUD systems that generates a virtual image.
2. Prior Art
References Cited:                [1] U.S. Pat. No. 7,623,560, El-Ghoroury et al, Quantum Photonic Imager and Methods of Fabrication Thereof, Nov. 24, 2009.        [2] U.S. Pat. No. 7,767,479, El-Ghoroury et al, Quantum Photonic Imager and Methods of Fabrication Thereof,        [3] U.S. Pat. No. 7,829,902, El-Ghoroury et al, Quantum Photonic Imager and Methods of Fabrication Thereof,        [4] U.S. Pat. No. 8,049,231, El-Ghoroury et al, Quantum Photonic Imager and Methods of Fabrication Thereof,        [5] U.S. Pat. No. 8,243,770, El-Ghoroury et al, Quantum Photonic Imager and Methods of Fabrication Thereof,        [6] U.S. Patent Application Publication No. 2010/0066921, El-Ghoroury et al, Quantum Photonic Imager and Methods of Fabrication Thereof,        [7] U.S. Patent Application Publication No. 2012/0033113, El-Ghoroury et al, Quantum Photonic Imager and Methods of Fabrication Thereof,        [8] U.S. Pat. No. 4,218,111, Withrington eta al, Holographic Heads-up Displays, Aug. 19, 1980.        [9] U.S. Pat. No. 6,813,086, Bignolles et al, Head Up Display Adaptable to Given Type of Equipment, Nov. 2, 2004.        [10] U.S. Pat. No. 7,391,574, Fredriksson, Heads-up Display, Jun. 24, 2008.        [11] U.S. Pat. No. 7,982,959, Lvovskiy et al, Heads-up Display, Jul. 19, 2011.        [12] U.S. Pat. No. 4,613,200, Hartman, Heads-Up Display System with Holographic Dispersion Correcting, Sep. 23, 1986.        [13] U.S. Pat. No. 5,729,366, Yang, Heads-Up Display for Vehicle Using Holographic Optical Elements, Mar. 17, 1998.        [14] U.S. Pat. No. 8,553,334, Lambert et al, Heads-Up Display System Utilizing Controlled Reflection from Dashboard Surface, Oct. 8, 2013.        [15] U.S. Pat. No. 8,629,903, Seder et al, Enhanced Vision System Full-Windshield HUD, Jan. 14, 2014.        [16] B. H. Walker, Optical Design of Visual Systems, Tutorial tests in optical engineering, published by The international Society of Optical Engineering (SPIE), pp. 139-150, ISBN 0-8194-3886-3, 2000.        [17] C. Guilloux et al, Varilux S Series Braking the Limits        [18] M. Born, Principles of Optics, 7th Edition, Cambridge University Press 1999, Section 5.3, pp. 236-244.        
Heads-up displays are being sought after as a visual aide technology that can contribute to automotive safety by making automobile drivers more visually aware and informed of the automobile dashboard information without taking their sight and attention off the road. However, currently available heads-up displays are volumetrically large and too expensive to be a viable option for use in automobiles. The same types of difficulties, though to a lesser extent in the cost factor, are encountered in applications of heads-up displays in small aircraft and helicopters. In the case of heads-up display automotive applications, the volumetric and cost constraints are further exacerbated by the wide range of vehicle sizes, types and price range. Therefore there is a need for low-cost and non-bulky heads-up displays that would be suitable for use in small vehicles such as automobiles, small aircraft and helicopters.
Prior art HUD systems can be grouped into two types; pupil imaging HUD and non-pupil imaging HUD. Pupil imaging HUD are typically comprised of a relay module, which is responsible for intermediate image delivery and pupil formation, and a collimation module, which is responsible for image collimation and pupil imaging at the viewer's eye location (herein referred to as the eye-box). The collimation module of a pupil imaging HUD is typically realized as a tilted curved or planar reflector or a holographic optical element (HOE) and the relay module is typically tilted for bending the light path and to compensate for optical aberrations. Non-pupil imaging HUD defines the system aperture by the light cone angle at the display or at the intermediate image location by diffusion. For intermediate image HUD systems, a relay module is also needed, but HUD aperture is decided by collimation optics alone. The collimation optics usually has axial symmetry but with folding mirrors to meet the volumetric constraints. This is decided by aberration correction needs and system volumetric aspects.
The prior art described in Ref [8], shown in FIG. 1-1, uses a concave HOE reflector (11 in FIG. 1-1) as a combiner and collimator to minimize collimation optics and reduce the HUD system volumetric aspect. The resultant HUD system needs complicated tilted relay optics (10 in FIG. 1-1) to compensate aberration and deliver an intermediate image. In addition, this HUD system works only for a narrow spectrum.
The prior art described in Ref [9], shown in FIG. 1-2, uses a relay optics (REL) module to deliver an intermediate image at the focal plane of convergent combiner (CMB) mirror (CMB in FIG. 1-2) and defines the system pupil. The CMB mirror collimates the intermediate image and images the system pupil onto the viewer's eye to facilitate viewing. This pupil imaging HUD approach always involves a complicated REL module for packaging and aberration compensation.
The prior art described in Ref [10], shown in FIG. 1-3, uses a projection lens (3) to project an intermediate image on a diffusive surface (51 in FIG. 1-3) as an image source and a semi-transparent collimating mirror (7 in FIG. 1-3). The collimating mirror forms an image at infinity and the aperture of the collimation optics is defined by the angular width of the diffuser.
The prior art described in Ref [11], shown in FIG. 1-4, uses an image forming source comprised of two liquid crystal display (LCD) panels (23 in FIG. 1-4) to form an intermediate image on a diffusive screen (5 in FIG. 1-4) which is placed at the focal plane of the collimation optics module (1 in FIG. 1-4). The main purpose of the two LCD panels in the image forming source is to achieve sufficient brightness for viewability of the formed image. In order to achieve that objective the two LCD panels in the image forming source are configured to either form two contiguous side by side images at the diffusive screen or overlap two images shifted from each other horizontally and vertically by a half pixel at the diffusive screen.
The prior art described in Ref [12] uses a pair of reflective holographic optical elements (HOE) to achieve holographic dispersion correction and to project a virtual image of a broadband display source within the observer's field of view. The prior art described in Ref [13] also uses a pair of holographic optical elements (HOE); one transmissive and another that is reflective to project an image onto the vehicle windshield.
The prior art described in Ref [14], shown in FIG. 1-5, uses an image projector (14 in FIG. 1-5) mounted on the topside of the vehicle windshield configured to project an image onto the vehicle dashboard equipped with a faceted reflective surface (18 in FIG. 1-5) with the latter being configured to reflect the image from the image projector onto the windshield of the vehicle. The vehicle windshield surface is oriented to reflect the image from the dashboard faceted reflective surface toward the viewer.
Common amongst the briefly described prior art HUD systems as well as the many others described in the cited prior art is the high cost and large volumetric size of the system. In addition, none of the found prior art HUD systems can be scaled in size and cost to match a wide range of automobiles and other vehicles' sizes and price ranges. It is therefore an objective of this invention to introduce heads-up display methods that use a multiplicity of emissive micro-scale pixel array imagers to realize a HUD system that is substantially smaller in volume than a HUD system that uses a single image forming source. It is further the objective of this invention to introduce a novel split exit pupil HUD system design method that utilizes the multiplicity of emissive micro-scale pixel array imagers to enable the realization of a modular HUD system with volumetric and cost aspects that can be scaled to match a wide range automobile and small vehicle sizes and price ranges. Additional objectives and advantages of this invention will become apparent from the following detailed description of preferred embodiments thereof that proceeds with reference to the accompanying drawings.